From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sylvain Lemieux Subject: Re: [PATCH] pwm: lpc32xx: Set PWM_PIN_LEVEL bit in lpc32xx_pwm_disable Date: Wed, 22 Jun 2016 09:26:04 -0400 Message-ID: <1466601964.5316.19.camel@localhost> References: <1464982677-24883-1-git-send-email-slemieux.tyco@gmail.com> <20160622123222.GD26943@ulmo.ba.sec> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20160622123222.GD26943@ulmo.ba.sec> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Thierry Reding Cc: linux-pwm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, vz@mleia.com List-Id: linux-pwm@vger.kernel.org Hi Thierry, On Wed, 2016-06-22 at 14:32 +0200, Thierry Reding wrote: > On Fri, Jun 03, 2016 at 03:37:57PM -0400, Sylvain Lemieux wrote: > > From: Sylvain Lemieux > > > > If the PWM_PIN_LEVEL bit is setup to 1 in the bootloader, when the kernel > > disable the PWM, the PWM output is always set as a logic 1. > > I presume there's a reason why the bootloader set this bit to 1. Why do > you assume it's the right thing to clear it? > There is an alternative mode for the PWM output pin; using the PWM_PIN_LEVEL bit to control the PWM output (logical 0 or 1 on output) when the PWM is disable. In this case, the bootloader is using the PWM_PIN_LEVEL bit to control the PWM output (always 1) to enable the LCD; the application is using the PWM to control the intensity of the LCD output. When disabling the PWM, the line level should be setup to 0. A version 2 of this patch will be send with support to select the alternate PWM disable level high from the device tree. For details, you can refer to: http://thread.gmane.org/gmane.linux.pwm/3882/focus=508758 Sylvain > Thierry